1. Field of the Invention
The present invention relates to an actuator latch apparatus of a hard disk drive for locking or unlocking an actuator of a hard disk drive.
2. Description of the Related Art
In general, a hard disk drive, as shown in FIG. 1, includes a hard disk 20 rotatably installed on a base 10 and on and from which predetermined information is recorded and reproduced. A hard disk also includes a magnetic head transfer apparatus for transferring a magnetic head 50 to a desired track position on the hard disk 20 to record and reproduce information. Here, the hard disk 20 is divided into a record area 22, where information is recorded, and a parking area 21 provided at the inner side of the hard disk 20, where the magnetic head 50 is disposed when the hard disk 20 stops rotating. The magnetic head transfer apparatus includes an actuator 30, where the magnetic head 50 is installed, capable of pivoting around a pivot shaft 34 provided on the base 10, a voice coil motor (not shown) for pivoting the actuator 30 by an electromagnetic force, and a latch apparatus for locking the actuator 30 after the magnetic head 50 is disposed in the parking area 21.
The actuator 30 includes a suspension portion 31 supporting the magnetic head 50, an arm 32 coupled to the pivot shaft 34 and capable of pivoting, and a bobbin portion 33. The voice coil motor, which will be described later, includes a moving coil 35 wound around the bobbin portion 33 and a magnet 41 attached to a yoke 40 installed at the base 10 to generate magnetic force.
Although not shown in the drawing, there are a pair of yokes 40 facing each other with the actuator 30 interposed therebetween. An electromagnetic force is generated by an interaction between the lines of a magnetic force generated by the magnet 41 and current flowing on the moving coil 35 so that the actuator 30 pivots in a direction according to Fleming's left hand rule.
The latch apparatus that locks the actuator 30 after the magnetic head 50 is disposed in the parking area 21 includes a magnetic member 43, installed at the yoke 40 and magnetized by the magnet 41, a damper 60 inserted in a coupling protrusion 36 provided at an end portion of the bobbin portion 33 of the actuator 30, and a steel piece 61 coupled to an end portion of the damper 60.
Accordingly, when the actuator 30 pivots and the magnetic head 50 installed at the suspension portion 31 enters the parking area 21 of the hard disk 20, as shown in FIG. 1, the steel piece 61 coupled to the side of the bobbin portion 33 adheres to the magnetic member 43. Thus, the actuator 30 maintains a state of being locked by a magnetic coupling between the steel piece 61 and the magnetic member 43 until an electromagnetic force for pivoting the actuator 30 is generated again.
The reason for locking the actuator 30 as described above is shown below. First, the suspension portion 31 supporting the magnetic head 50 provides an elastic force in a direction that keeps the magnetic head 50 in close contact with the surface of the hard disk 20. Thus, the magnetic head 50 maintains a state of closely contacting the surface of the hard disk 20 unless an external force is applied. However, when the hard disk 20 starts to rotate, air flow is generated around the magnetic head 50 by the rotation of the hard disk 20. The air flow generates aerodynamic lift, thereby causing the magnetic head 50 to lift from the horizontal surface of the hard disk 20. Since the hard disk 20 is rotating when information is recorded in the record area 22 of the hard disk 20 or information is read therefrom, the magnetic head 50 is in a non-contact state separated a predetermined distance from the horizontal surface of the hard disk 20. Therefore, scratches due to friction between the magnetic head 50 and the record area 22 are not generated. But, when the rotation of the hard disk 20 is completely stopped, for example, when power is turned off, since the lift lifting the magnetic head 50 disappears, the actuator 30 pivots so that the magnetic head 50 can be positioned in the parking area 21 before the lift disappears.
In the above conventional latch apparatus, however, since the actuator 30 is locked by a (force of magnetically) magnetic coupling between the steel piece 61 and the magnetic member 43. When a impact greater than the magnetic force is applied in the locking state, the locking is released. In contrast, to release and pivot the locked actuator 30, the electromagnetic force generated by the moving coil 35 and the magnet 41 must exceed the coupling force between the steel piece 61 and the magnetic member 43. Thus the coupling force cannot be too great, because it would maintain the actuator 30 in a locked state and keep it from pivoting. In other words, when the magnetic coupling force between the steel piece 61 and the magnetic member 43 is too small, the locking is easily released by a small external impact, and when the magnetic coupling force is too great, the locking is not released and the actuator 30 is prevented from pivoting.
Further, in the above structure, when the locking is released by overcoming the magnetic coupling force, since the actuator 30 rapidly springs off at a high speed because of inertia, the coupling protrusion 36 may strongly collide against a stopper 42 provided at the opposite direction of the magnetic member 43. Collision between the actuator 30 and the stopper 42 may generate a head slap. To restrict the head slap, applying current to the moving coil 35 is controlled so that a braking force is applied to the actuator 30 at the same time it is unlocked. But it is difficult to configure a control system since accurate control of the timing is difficult. Also, since a repetitive stress is applied to the damper 60 by the repeated actions of locking and unlocking, the damper 60 may be damaged.